Optical glass



Patented Feb. 17, 1 948 t i., poration, of NewYork :invention relates-tonopticalglass compositions 'fandparticularly tow compositions which have anfindexrof ref-ractionfor the Dline=(nD) greater than 1.60. and which are-suitable for use in .opticalginstruments and devices .of various 6 Hereto'fore the.. most common,V optical glasses'- having arefractive index greater-thanA 17.60 have been the .sox-called dense ilintprflead-glasses cadmiumv` borate glasses 'Y consisting practically entirely. 'of cadmiumioxide,`boric oxide and'V bery1'' f lium or aluminum oxide but free from silica have ther-@desired *optical*l properties. The i prior cadmium *containing glasses are not suillciently Y stable and resistantto 'devitrilcat'ion"fory my purposes.- and tend tocrystallizewhen annealed I orreworkedfforf'the .fabrication o f lenses `and other'opticalparts.r This" tendency toward 'de'-- vitrification increases with Ithe cadmium -content and-prevents th 'successful fabrication of glasses containing more than 'about 60%' CdO and hav- Y lng refractive indicesiabo've about v1.70.

The -primaryob'ject ofthisinvention is to pro'' vide new and useful opticalglasses.

Another'objctis'to" provide glasses which have an-index 'of"refractin '(nlD' greater than"1.60i and' a dispersiveide'x nl" higher than jhashere-V toforebeenhbtainable in the wellfknown alkali` lead `silicate Vglasses fof;v high 'refractive' in'dex;

Another f'object -:is to' provide "optical 4glasses having fthe 4'above optical' properties, which are Y compilsedfoi."non-volatile materials, can be melted and *fined easily `andare relatively cheap. f

Another object?l is ltoprovi'd'e optical glasses contaningrlarge percentages 'of cadmium oxide which are chemicallystableand highlyjesistant I to devitrication.

ApplicationSeptember@1945. Serial Nol-614,208

' 1s'cisims. (Chiuse-52) Other objects will hereinafter appear-'.5

I have found that certain silicateglasses with high cadmiumcontents'shave the vdesired optical vproperties as willherenafter apparl and also have improved chemical durability and greatly, increased resistance to devitrifhation. Byf means t of the invention,V stable glasses can be produced which have cadmium contents asjhighas 80% CdO and refractive indices ashighas 'about '1.8 and which willnot devitrif'y when rehated toA softness for molding. AThe new glasses must con-vY tain at least ,20% -CdOand at least 2% S102.

Preferably they-should alsocontain at least 2% A1203 and at least 2% B203. VThe B203 should not exceed 40% `ati the most and preferably` should not exceed about'15%, and may be en- Y l tlrely cmittedwhen CdO is less than about '10%.`

Y Alumina, onthe Aother hand, should not' exceed about 30% and may be omitted when CdO is In other words. the new glasses broadly 'comprise A20% `to t80% CdO. 2%" to SiOzi, 0% to 30%A12O3fand 0% .to 40%' .-BzOs. 'Y

more than about I have further found that substantial amounts of the divalent oxidesyof the heavy metals, lead..

amounts" ofalkalilmetal oxides (R)A not ex` a.o ceeding about 20%, and small amounts of zireonia, can be introduced intof-the above glasses with advantageous improvements in stability'and optical properties. -Iri case'xthe glassesfcontainV substantial amounts of 'additional vmetal oxides,` such as PbO or R20, both the' alumina and boric oxide maybe lomitted if desired without seriously affecting the stability-or opticalproperties'. fl The* i presence of zirconia inalrlounts' as` large as 5%" or more necessitatesa decrease' in theamount'bf alumina in order for the zirconia to' become dis'- solved in the glass. Other'oxides which 'are commonly used in optical glass compositions such Vas BeO, `ZnO, TiOz, etc.; may also`b'e included in' the` new glasses without departin'g'ifromtthe spirit -and scope of the invention as claimed;V

cent byweight as calculatedfromjtheir respective batches, s how by way of example composl-` tions which" 1I have melted' and which fall within 750 the Scope 0f my invention.

The above glasses ,are chemicallyista'ble Aand resistant to devitrlfication when yheated toA` softi'v nessfor molding.; It will be noted that they have refractive indices' greater than '1.60, and relatively`v high-"dispersive indices.j

To illustrate theA relationship lbetween fnD and@ n for lthe' -glassesifof lthis invention; reference vis4` had to the accompanying drawing'whieh -is an` diagram representing the-value --of mD forf-thel above glasses plottedagainstL their "respective-1 valuesl off and;#designated-bythe letters of lthekrv respective glasses It' `Wi1lff-bel notedfthat the values for the" variousl glassesare above the-lines .u X and-Yiwhich representthe approximateminima in the-va1ues:for nDand A11 whichcharacterize the glasses ofthisinvention. i,

The rliney Xiisf: v drawn s through :zthezfu pointsf (nDlO, z2:42). .and;.(nD=^1.70, =v=322)5 andI -1 defined by the equation I claim:

1. ffA. transparent.:optical; glass `which 'contains 1; 20%eto:f,80% CdO,.2%fito1,50l% Si02;=10 ".to' '30%21 A1263 aand to 540%?B2Oa* and :which hasfam index' oferefraction fiorgthe; fDline'..f,(1/Ll3).jl .oi at,y i, leastz1.60. and la dispersive.v index uit greater, than 1 both :v 2021400 nDand 11=111.4+;.46f.6 nD.

2.,A if transparent optical? glassewhich :contains ii 20 tov.80:%CdO, 42%sto 50%Si02, and '2%"ztoa 40% -B2Os.-fand which has anfindexpf refraction-i; for the Diline- (11D)I of i atleast'` 1.60; and. a dispei-f'- sive index 2). ,greaterA than; both '12:202.;1003;nD1- f and v=v111.4.-46.6 'n.D;.:

3. A transparent@ ,opticalglassf ,which containst :x70

20%,.to 80% vCdO,.-2%.to 50% Si02, and 2% tozA 15%B2Oa`, anciwhich has anindex. ofrefractionttfor the..D.line.-(11.D).l of@at.,least,.1.60and avdisper-` 4. A transparent optical glass which contains 20% to 80% CdO, 2% to 50% SiOz, 2% to 30% A1203 and 2% to 40% B203, and which has an index of refraction for the D line (11D) of at least 1.60 and a dispersive index (v) greater than both 11:202-100 nD and v=111.446.6 nD.

5. A transparent optical glass which contains 20% to 80% CdO, 2% to 50% S102, and up to 55% PbO, and which has an index of refraction for the D line (nD) of at least 1.60 and a dispersive index (v) greater than both v=202100uD and v=111.4-46.6 nD.

6..A Atransparent opticahglasswhich contains 20%#tow80%ffiCd0.s2% to;,50%i SiOn up to; .f55%

15 PbO, and 2% to 40% B203, and which has an index of refraction for the D line (nD) of at least 1.60`and a dispersive index (v) greater than both i''=2 02.f100 nD and v=111.446.6 nD.

'7. A transparent optical glass which contains Pb0.fand2%``to 15.%TB202, and which has an index oi refraction for the D line (nD) of at least 1.60andadispersivelindex (v) greater than both v=202..100.-1zD and v=111.446.6 nD.

8."A transparent opticalfglass which contains to 80% CdO. 2% to'50% Si02, zroz. and.

2%"to 40% B202, and which Yhas-an index otre-r fraction' for v'theV D "line I`(nDY' of' at "least I1,60

and a f vzlispersivey index A 1( u)k greater/than 4both e' 9.-"A transparent voptical glass which" contains 'i 20% to vv80% CdO, 2% to 50% S102, .1% to 20%" alkali metal oxide;A and' Jwhich )hasA an f index 'of refraction for -the DI line (nD) of at least 1.60' and "a dispersive index iV 'greater than A`both alkali meta-l oxide,-'and-2%"'to30%"Al20i1and 4whichlhas an indexfof'refraction for the D2iine3 (11D) 'fofatleast 1.60'and a dispersive indexA v(if) whichhas anfindexof refractio'nffor the Dline (12D) fof at.1east 1.60and 7"a dispersiv'efindex--i 11).

12. -A transparent: optical glassnwhich conta-insv :n

alkali metall-oxide,4 andup, to: PbO; and ,which 13. -.Atransparent optical l.glassrwhich container..

indexl -of'A refraction for-:fthe D line, 11D)` of s :at: 1:

least 1.60v andl -a `dispersivefindex v) Igreater lthan@ 15,.. `.Atransparenty optical'giass .which container.v

for theAD .line-(nD)-of;at least-1.60fanda disperde.. sivev index (2)greater;thanfb0thw=2021-100 111355 7,5 .and mure-46.6 nn.

5 6 16. A transparent optical glass which contains CITED 20% to 80% CdO. 2% to 50% S102. .1% to 20% REFERENCES alkali metal oxide. up to 55% Pbo and 2% to The following references are of record in the 30% A1203, and which has an index of refraction file 0f this Patenti for the D line (11D) of at least 1.60 and a disper- 5 sive index m greater than both y=2o21oo nn UNITED 'STATES PATENTS and v=111.446.6 nD. Number Name Date WILLIAM n. ARMIsmAD. 2,298,746 Moulton Oct. 13, 1942 Disclaimer 2,435,995.W'Zh'am H. Armz'stead, Corning, N. Y. OPTICAL GLASS. Patent dated Feb. 17, 1948. Disclaimer led Nov. 20, 1951, by the assignee, Oor/ning Glass Works. Hereby enters this disclaimer to claims 1, 2, 5, and 6 f said patent.

[Official Gazette December 25, 1.951.] 

